Why the artificial moon of China will probably not work

Going out on a moonlit night, it's seeing the darkness pushed back. The sunlight reflected by our natural satellite during an almost full moon is sufficient to file the silver night landscape and even allow a human eye to penetrate into the darkness. But we can always do better, right? If a moon is good, two, it's even better.

A Chinese researcher thinks so. Wu Chunfeng, chairman of the Science Society of the Tian Fu New Area, wants to use a satellite as an artificial moon, sending sunlight back to targeted areas of the Earth at night. The reflector would orbit over a city and provide enough lighting to replace the ground lighting with a constant glow and thus save electricity.

Illuminate the night

He imagines a brilliant satellite moving in space about 300 miles above the ground and moving towards the cities on the ground. One would be enough to light about 5o square miles, he says, according to China Daily, and several working in concert could clear up to 4000 square miles. According to Wu, the first should be ready for launch in 2020 and three more by 2022, although details of the project remain largely unknown.

According to satellite experts, the plan may not be so simple. Based on the meager details available, the satellite would probably never work, said Ryan Russell, an associate professor of aerospace engineering at the University of Texas at Austin.

The biggest defect? A satellite flying low enough to provide as much light could not stay in one place.

"Their claim for 1 LEO sits at [300 miles] must be a misinformed typo or spokesperson, "says Russell in an email. "The article I read implied that you could fly over a satellite over a particular city, which of course is not possible."

Satellites that remain above a fixed point on the Earth, what is called a geostationary orbit, sit much further away: about 38,000 miles. At this distance, the reflective surface should be very wide so that humans can see enough light to return to Earth. At a distance of barely 300 miles, the moon was circling the Earth thousands of kilometers at the hour, projecting its light on a given place for a fraction of a second.

Iain Boyd, professor of aerospace engineering at the University of Michigan, could maintain an artificial moon in place thanks to rocket boosters.

A constellation of satellites circling the Earth would be needed to keep the lights on all night, exchanging reflexive functions with each other when they passed overhead. And even in this case, fuel is needed to counter the small atmospheric drag present even in the low orbits above the Earth. The International Space Station, for example, gravitates about 250 km and must be constantly recalled in its orbit because it slows down because of the drag.

The costs of launching and refueling several satellites would likely far exceed electricity savings, at least for now.

Turn off the lights

There is also the question of whether we want a nightlight throughout the city in the first place. Some cities around the world are already trying to reduce light pollution by making their nights darker, not clearer. An excess of nocturnal light disrupts the activities of nocturnal animals, blocks the stars and could even interfere with our circadian rhythms and have an impact on health.

If we really need better lighting solutions, it might be better to focus on more earthly options, Russell says.

"It's a very complicated solution that affects everyone with a simple problem that affects a few. It's light pollution on steroids, "he says. "And they illuminate the whole surface, while streetlights light the streets to light. Imagine whole generations of people living in the same urban areas without ever seeing the stars at night? "